@khird #1 is an issue regardless of tagging. If your a new user you have no followers, so you wont get many people who see what you post regardless. With that said, there is no reason to think you **need** tags to be seen. Many users would likely still view a feed that is inclusive of all posts and only **exclude** tags rather than use an exclusive feed and select **inclusive** tags. Ultimately, the power is with the user what they want to see. just as some users view an unfiltered federated fee now.
#2 Yes people will try. Any intelligently designed system will, however, prevent that. Stackoverflow uses the system I provided and because it is well designed prevents issue #2, not to mention prevents issue #1 with its designs as well.